Influenza vaccinations: who needs them and when?

Influenza vaccination programmes should aim at reducing the burden from influenza among those who need it most. The primary aim of this literature review is to identify who should receive priority in influenza vaccination programmes. Risk factors for severe post-influenza complications include immune-related factors, such as ageing or the presence of immune-suppression, respiratory tract disease, proneness to exacerbation of concomitant high-risk disease, potential adverse effects associated with long-term drug use or residence in closed communities with high transmission rate. When given annually in autumn, inactivated trivalent influenza vaccines can reduce severe complications from influenza among persons aged 65 years or older by 30-60%. Among children aged less than 7 years, notably those with asthma, the occurrence of otitis media or acute respiratory disease is reduced by 20-75% with vaccination. In addition, vaccination of residents of long-term care facilities and their personnel leads to a 42% reduction in mortality among patients. However, uncertainty remains about whether influenza vaccination can reduce complications from influenza among the large group of older children and persons of working-age with high-risk disease. To further increase the impact of prevention strategies, the development and application of clinical prediction rules to estimate absolute risks of post-influenza complications should be studied in relation to optimal vaccine delivery strategies. Furthermore, adequately powered studies should be conducted to demonstrate possible effectiveness of vaccination in reducing post-influenza complications among older children and working-age adults.